Detection of proteins that signal the presence or recurrence of cancer is a powerful therapeutic tool for effective early diagnosis and treatment. Carcinoembryonic antigen (CEA) has been extensively studied as a tumor marker in clinical diagnosis. We report on the development of an amperometric biosensor for the detection of CEA based on the immobilization of anti-CEA monoclonal antibody on a novel class of bipodal thiolated self-assembled monolayers containing reactive N-hydroxysuccinimide (NHS) ester end groups. The current variations showed a linear relationship with the concentration of CEA over the range of 0-200 ng/mL with a sensitivity of 3.8 nA.mL.ng(-1) and a detection limit of 0.2 ng/mL, which is well below the commonly accepted concentration threshold (5 ng/mL) used in clinical diagnosis. Real time and accelerated stability studies of the reporter antibody under various storage conditions demonstrated that the enzymatic activity and antibody affinity of the conjugate is retained for long periods of time in commercial stabilizing buffers such as StabilGuard Biomolecule Stabilizer, and a prediction of the stability trends was carried out using the kinetic and thermodynamic parameters obtained from the Arrhenius equation. The developed immunosensor as well as a commercially available enzyme-linked immunosorbent assay (ELISA) kit were successfully applied to the detection of CEA in serum samples obtained from colon cancer patients, and an excellent correlation of the levels of CEA measured was obtained. Ongoing work is looking at the incorporation of the developed biosensor into a platform for multiplexed simultaneous detection of several breast cancer related biomarkers.